[Mp4-tech] [audio] audio thinning

[Dave Singer]

At 1:28 AM -0700 9/8/04, Sunil Bhargo wrote:
>Hi,
>	I have a very basic question , is it possible for audio to have
>key frames (I frames) and if so when we thin does it follow the same
>thinning rules as video (that only key frames will be sent).
>
>sunil bhargo

in all audio codecs we have at the moment, I think that all frames 
are in a sense I frames.  If you discard frames, you discard sections 
of time, however.  In video, a succession of still pictures are 
displayed;  if you thin, then the motion becomes jerky, but as each 
frame is displayed for the full duration up to the next frame, the 
video is continuous.  That's not true if you discard audio frames.
It's also worth noting that in AAC, each frame is only correctly 
decoded (perfectly decoded) if the frame before it was also decoded. 
The transform is longer than the frame size.
>
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-- 
David Singer
Apple Computer/QuickTime